AMGEN INC. v. AMNEAL PHARM. LLC, Appeal No. 2018-2414 (Fed. Cir. Jan. 7, 2020).  Before Newman, Lourie, and Taranto.  Appealed from D. Del. (Judge Goldberg).  (Claim Construction; Prosecution History Esptoppel)


Amgen has a patent covering its drug Sensipar®, which is a formulation of cinacalcet hydrochloride used to treat hyperparathyroidism in patients with chronic kidney disease or cancer.  Defendants Amneal and Primal each filed an ANDA for a generic version of Sensipar®, and Amgen brought suit against each of them for infringement.

At issue in the district court was the construction of a Markush group and whether the acceptance of an Examiner’s Amendment to add the Markush group triggered prosecution history estoppel to bar infringement based on the doctrine of equivalents.

Claim 1 of the patent used the transitional phrase “comprising” and the Markush group recited “at least one binder selected from the group consisting of” (emphasis added).  The district court construed the claim as being closed to unrecited binders based on the “consisting of” language.  Therefore, because Amneal’s formulation included both a recited binder and an unrecited binder, Amneal did not literally infringe Amgen’s patent.

Further, the district court concluded that the acceptance of the Examiner’s Amendment was for reasons relating to patentability, and thus prosecution history estoppel barred the application of the doctrine of equivalents to a formulation that only used an unrecited binder.  Therefore, Primal did not infringe because its formulation only used an unrecited binder.


Was the claim correctly construed?  Did prosecution history estoppel apply?  (continue reading)

Summary by:  Jason French

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